• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.263-268
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• 2003

The Electrical insulation design and testing of high temperature superconducting (HTS) coil for high temperature superconducting fault current limiter (HTSFCL) has been performed. Electrical insulating factors of HTS coil for HTSFCL are turn-to-turn, layer-to-layer. The electrical insulation of turn-to-turn depends on surface length, and the electrical insulation of layer-to-layer depends on surface length and breakdown strength of L$N_2$. Therefore, two basic characteristics of breakdown and flashover voltage were experimentally investigated to design electrical insulation for 6.6㎸ Class HTSFCL. We used Weibull distribution to set electric field strength for insulation design. And mini-model HTS coil for HTSFCL was designed by using Weibull distribution and was manufactured to investigate breakdown characteristics. The mini-model HTS coil had passed in AC and Impulse withstand test.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.617-618
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• 2012

Recently as the inactive response characteristics of the existing RCD(Residual Current protective Device) used on low voltage power distribution system, so control of overload and electric short circuit faults, major causes of electrical fires, are not enough. Therefore, this paper is proposed a prevention apparatus using neutral line voltage and semiconductor switching devices for the prevention of electrical disasters in low voltage power distribution system caused by overload or electric short circuit faults. The proposed prevention apparatus confirms the excellent characteristics in response velocity and accuracy in comparison with the conventional circuit breaker(RCD) through various operation performance analysis.

• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.52-55
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• 2010

A sub-cooled liquid nitrogen system is known as a promising method to develop high voltage superconducting apparatuses such as superconducting fault current limiters (SFCLs) and superconducting cables. To develop a high voltage superconducting machine adopting the sub-cooled liquid nitrogen system with a constant pressure. injecting a non-condensable gas is indispensable. In this study. the dielectric characteristics of insulation gases are investigated and analyzed by using electric utilization factors ($\xi$). It is found that the maximum electric field at sparkover that occurs with 50 % probability. $E_{MAX.50%}$ exponentially decreases as the S increases. This means that the $E_{MAX.50%}$ at sparkover can be estimated with the $E_{MAX.50%}$

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.1006-1008
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• 1997

This paper presents the logic based High Impedance Fault(HIF) detection rules for distribution lines. Due to the characteristics of HIF, which shows low current on relaying points, it is difficult to detect the fault occurred in distribution line by the conventional overcurrent relay(OCR) and/or harmonics relay. The HIF data were generated by using TACS in EMTP. In this paper, The harmonic index is defined as the ratio of harmonic component to fundamental component. The proposed HIF detection rules are obtained by analysing the difference between normal condition and HIF condition.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.396-404
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• 2011

This paper proposes a performance improvement of a grid-connected wind turbine using sliding-mode based direct power control under an unbalanced grid fault. The proposed control method has some advantages for grid connected control. At first, it doesn't need the synchronous phase angle of the grid voltage. It has also fast dynamic characteristics compared with a conventional current controller. In addition, it is suitable for an unbalance compensation control. The effectiveness and robustness of the proposed algorithm are verified by simulations and experiments.

• Nuclear Engineering and Technology
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• v.51 no.2
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• pp.444-452
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• 2019

To assess the availability of a nuclear power plant's dynamic systems, it is necessary to consider the impact of dynamic interactions, such as components, software, and operating processes. However, there is currently no simple, easy-to-use tool for assessing the availability of these dynamic systems. The existing method, such as Markov chains, derives an accurate solution but has difficulty in modeling the system. When using conventional fault trees, the reliability of a system with dynamic characteristics cannot be evaluated accurately because the fault trees consider reliability of a specific operating configuration of the system. The dynamic reliability graph with general gates (DRGGG) allows an intuitive modeling similar to the actual system configuration, which can reduce the human errors that can occur during modeling of the target system. However, because the current DRGGG is able to evaluate the dynamic system in terms of only reliability without repair, a new evaluation method that can calculate the availability of the dynamic system with repair is proposed through this study. The proposed method extends the DRGGG by adding the repair condition to the dynamic gates. As a result of comparing the proposed method with Markov chains regarding a simple verification model, it is confirmed that the quantified value converges to the solution.

• Earthquakes and Structures
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• v.8 no.6
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• pp.1363-1386
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• 2015

The October 23 2011 Van Earthquake is studied from an earthquake engineering point of view. Strong ground motion processing was performed to investigate features of the earthquake source, forward directivity effects during the rupture process as well as local site effects. Strong motion characteristics were investigated in terms of peak ground motion and spectral acceleration values. Directiviy effects were discussed in detail via elastic response spectra and wide band spectograms to see the high frequency energy distributions. Source parameters and slip distribution results of the earthquake which had been proposed by different researchers were summarized. Influence of the source parameters on structural response were shown by comparing elastic response spectra of Muradiye synthetic records which were performed by broadband strong motion simulations of the earthquake. It has been emphasized that characteristics of the earthquake rupture dynamics and their effects on structural design might be investigated from a multidisciplinary point of view. Seismotectonic calculations (e.g., slip pattern, rupture velocity) may be extended relating different engineering parameters (e.g., interstorey drifts, spectral accelerations) across different disciplines while using code based seismic design approaches. Current state of the art building codes still far from fully reflecting earthquake source related parameters into design rules. Some of those deficiencies and recent efforts to overcome these problems were also mentioned. Next generation ground motion prediction equations (GMPEs) may be incorporated with certain site categories for site effects. Likewise in the 2011 Van Earthquake, Reverse/Oblique earthquakes indicate that GMPEs need to be feasible to a wider range of magnitudes and distances in engineering practice. Due to the reverse faulting with large slip and dip angles, vertical displacements along with directivity and fault normal effects might significantly affect the engineering structures. Main reason of excessive damage in the town of Erciş can be attributed to these factors. Such effects should be considered in advance through the establishment of vertical design spectra and effects might be incorporated in the available GMPEs.

• Journal of the Korea Convergence Society
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• v.2 no.2
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• pp.47-56
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• 2011

Korea Ministry of Knowledge Economy has estimated that wind power (WP) will be occupied 37% in 2020 and 42% in 2030 of the new energy sources, and also green energies such as photovoltaic (PV) and WP are expected to be interconnected with the distribution system because of Renewable Portfolio Standard (RPS) starting from 2012. However, when a large scale wind power plant (over 3[MW]) is connected to the traditional distribution system, protective devices (mainly OCR and OCGR of re-closer) will be occurred mal-function problems due to changed fault currents it be caused by Wye-grounded/Delta winding of interconnection transformer and %impedance of WP's turbine. Therefore, when Double-Fed Induction Generator (DFIG) of typical WP's Generator is connected into distribution system, this paper deals with analysis three-phase short, line to line short and a single line ground faults current by using the symmetrical components of fault analysis and PSCAD/EMTDC modeling.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.10
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• pp.793-797
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• 2010

The basic performance of the ground system is evaluated as the ground resistance by applying low frequency current below 1 kHz. However, characteristics of the ground system should be analyzed by high frequency current up to 1 MHz since transient currents having a few hundred kHz component flow during a line-to-ground fault and/or a lightning strike. This paper deals with the design and fabrication of a wideband ground impedance meter (WGIM) which measures the impedance of ground systems in ranges from 65 Hz to 1.28 MHz. Also, a noise elimination algorithm using a digital bandpass filter is proposed. The maximum error of the WGIM is 4.91% in the measurement frequency range.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1998-1999
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• 2007

Before applying the HTS(High Temperature Superconductor) power devices to a real utility network, system analysis should be carried out by some simulation tools. PSCAD/EMTDC simulation tool is one of the most popularized useful analysis tools for electrical power system. Unfortunately the model component for HTS coil is not provided in PSCAD/EMTDC simulation tool. In this paper, EMTDC model component for HTS coil has been developed considering real characteristics of HTS coil like critical current, temperature and magnetic field. The developed model component of HTS coil could be used for power system application. Using the developed model component for HTS coil, we can easily do the simulation of HTS power devices application test in utility with the various inductance, quench current, inner magnetic field, and temperature values, for instances; SMES(Superconducting Magnetic Energy Storage) system, superconducting motor, transformer, and FCL(Fault Current Limiter)